The present invention generally relates to valves and methods for fabricating them and, in a preferred embodiment thereof, more particularly relates to rotary valves, such as "butterfly" valves, and associated valve fabrication methods.
Rotary valves, also commonly referred to as "butterfly" valves, are typically provided with a shut-off disc which is rotationally drivable between open and closed positions about an axis diametrically extending across the interior of a generally annular valve body. In its open position the disc permits fluid flow through the valve body, and when the disc is rotated to its closed position its periphery is brought into operative engagement with an annular seal member, which is part of an annular seal cartridge structure supported by the valve body, to shut off further fluid flow through the valve and piping sections that are suitably secured to opposite sides of its body portion.
Although rotary valves of this general type have been utilized for many years in both fluid throttling and shut-off applications, and have been refined in a variety of manners over this time span, they are still subject to several well-known problems, limitations and disadvantages. For example, rotary valve discs are customarily formed as a segment of a sphere and thus have a rounded peripheral seating surface. Because of this conventional disc configuration it is often difficult to reliably and accurately conform the valve seal to the peripheral disc seating surface without undesirably stretching the seal element to a substantial degree. Due to this geometric seal/seat interface problem the integrity of the seal is often compromised and it is difficult to completely stop the flow of fluid through the valve.
Because the periphery of the disc is used as the seal contact surface for the valve, it is critical to proper seal performance that the disc be precisely centered within the valve body. To this end, various structures have been incorporated into conventional rotary valve assemblies to permit the installed disc to be adjusted within the valve body in a manner effecting this necessary disc centering. This centering adjustment, of course, must be carefully and accurately performed to achieve the desired sealing effectiveness. Adjustment error, on the other hand, can seriously reduce the valve's sealing efficiency.
Another limitation present in rotary valves of conventional construction is related to the manner in which an actuator, a motorized device used to forcibly rotate the closure disc between its open and closed positions, is operatively mounted on the valve. In rotary valves of conventional construction an actuator base structure is formed integrally with the valve body (or permanently secured to as by welding) and projects radially outwardly from the valve body. In order to mount an actuator on the valve, an adapter structure is interposed between the actuator and the outwardly projecting base structure and secured to the actuator and base structure. This overall adapter mounting structure undesirably adds to the construction cost of the overall valve assembly and makes the fabrication of the assembly more complex and time-consuming.
As can readily be seen from the foregoing, a need exists for an improved rotary valve assembly, and associated fabrication methods therefor, which eliminate or at least substantially reduce the above-mentioned problems, limitations and disadvantages typically associated with rotary valves of conventional construction as generally described above. It is to this need that the present invention is directed.